The Policy and Charging Control (referred to as PCC) architecture of 3GPP (3rd Generation Partnership Project) is a function framework that can be applied to multiple access technologies, for example, it can be applied to the Universal Mobile Telecommunications System (referred to as UMTS) Terrestrial Radio Access Network (referred to as UTRAN), the Global system for Mobile Communication (referred to as GSM)/GSM Enhanced Data rates for Global Evolution (referred to as EDGE) radio access network, interworking wireless local area network (I-WLAN) and the Evolved Packet System (referred to as EPS), and so on.
FIG. 1 is a diagram of a Rel-8 PCC non-roaming architecture in the related art, in the following, functions of each logical function entity and its interface in the PCC architecture will be described with reference to FIG. 1: the Application Function (referred to as AF) entity provides a access point for service applications, and network resources used by these service applications need dynamic policy control. When performing the parameter negotiation in the service plane, the AF sends the relevant service information to the Policy and Charging Rules Function (referred to as PCRF) entity. If the service information is consistent with the PCRF policy, the PCRF accepts the negotiation; otherwise, the PCRF rejects the negotiation and in the feedback gives the service parameters acceptable by the PCRF. Subsequently, the AF returns these parameters to the user equipment (referred to as UE). The interface between the AF and the PCRF is the Rx interface.
The Policy Control and Charging Rules Function (PCRF) entity is the core of the PCC and it is responsible for making the policy decision and charging rules. The PCRF provides network control rules based on the service data flow, and these network controls comprise service data flow detection, Gating Control, quality of service (referred to as QoS) control and charging rules based on the data flow. The PCRF sends the made policy and charging rules to the Policy and Charging Enforcement Function (referred to as the PCEF) entity to enforce, and at the same time, the PCRF also needs to ensure that these rules are consistent with the user subscription information. The basis of the PCRF making the policy and charging rules comprises: acquiring the service-related information from the AF; acquiring the policy and charging control subscription information with the user from the user Subscription Profile Repository (referred to as SPR); acquiring the bearer-related network information from the PCEF.
The policy and control enforcement function (PCEF) entity is usually located in the Gate-Way (referred to as GW), the policy and charging rules made by the PCRF are enforced in the bearing plane. The PCEF detects the service data flows in accordance with the service data flow filter in the rules sent by the PCRF, and further enforces the policy and charging rules made by the PCRF on these service data flows. When establishing the bearer, the PCEF performs the QoS authorization in accordance with the rules sent by the PCRF and performs the gating control in accordance with the enforcement of the AF. According to the charging rule sent by the PCRF, the PCEF enforces the corresponding charging operation of the service data flow, and the charging is either online charging or offline charging. If it is the online charging, the PCEF needs to perform credit management with the online charging system (referred to as OCS). If it is the offline charging, the relevant charging information is exchanged between the PCEF and the offline charging system (referred to OFCS). The interface between the PCEF and the PCRF is the Gx interface, the interface between the PCEF and the OCS is the Gy interface, and the interface between the PCEF and the OFCS is the Gz interface. The PCEF is generally located in the network gateway, such as the GPRS Gateway Support Node (GGSN) in the GPRS and the Packet Data Gateway (referred to as PDG) in the I-WLAN.
The functions of the Bearer Binding and Event Reporting Function (referred to as BBERF) entity comprise bearer binding, upstream bearer binding verification, and event reporting. When the UE accesses through the E-UTRAN, and the PMIPv6 protocol is used between the Serving Gateway (referred to as S-GW) and the Packet Data Network Gateway (referred to as P-GW), the BBERF is located in the S-GW; when the UE accesses through the trusted non-3GPP access system, the BBERF is located in the trusted non-3GPP access gateway; and when the UE accesses through the un-trusted non-3GPP access system, the BBERF is located in the Evolved Packet Data Gateway (referred to as ePDG). At that moment, the PCEF no longer enforces the bearer binding function.
The SPR stores the user policy and charging control subscription information related to the policy control and charging. The interface between the SPR and the PCRF is the Sp interface.
The OCS and the PCEF together control and manage the user credit under the online charging mode.
The OFCS and the PCEF together finish the charging operation under the offline charging mode.
The PCC architecture, through each of the above function entities, realizes the policy and charging control of the IP Connectivity Access Network (referred to as IP-CAN) established by the UE for accessing one Packet Data Network (referred to as PDN).
In the packet system (such as EPS, UMTS, and so on), the bearer is the basic unit for the network providing the QoS guarantee to the service data flow transmission. Different bearers have different QoS Class Identifiers (referred to as QCIs) and Allocation and Retention Priorities (referred to as ARPs), and the service data flows transmitted in the same bearer have the same QCI and ARP. Each network element in the packet network adopts the same packet forwarding and processing mechanism to the service data flows transmitted in the same bearer, and adopts different packet forwarding and processing mechanisms to the service data flows transmitted in different bearers. The PCC architecture realizes the policy control of the packet system by establishing, modifying and terminating the bearers with different QoS capabilities. The bearers usually can be initiated, established, and controlled by the network or the UE. Currently, in the PCC architecture, there are two bearer control modes: UE_Only and UE_NW. The UE-Only indicates that all the bearers in the IP-CAN session established by the UE must be controlled by the UE, that is, the UE decides the establishment, modification and release of the bearers. The UE-NW indicates that the bearers in the IP-CAN session established by the UE can be controlled by the UE or the network, that is, either the UE or the network can decide the establishment, modification and release of the bearers.
In the current techniques, the protocol adopted in the PCC architecture is the Diameter application protocol developed on the basis of the Diameter Base Protocol, for example, the application protocol used in the Gx interface, the application protocol used in the Rx interface, the application protocol of the Gxx interface (including Gxa and Gxc interfaces) and the application protocol used in the roaming interface S9. In these application protocols, messages, commands, and AVP (Attribute Value Pairs), and so on used for the PCC are defined. Diameter sessions established with these protocols can respectively become Gx session, Gxx session, Rx session and S9 session. Each function entity of the PCC performs the policy and charging control, through these sessions, to the PDN connection established when the UE accesses the network.
FIGS. 2 and 3 are structural diagrams of the PCC respectively in two roaming scenarios of home routed and local breakout. The PCRF in the home network (i.e., Home Public Land Mobile Network (HPLMN)) is the hPCRF (home policy control and charging rules function entity), and the PCRF in the visited network (i.e., Visit Public Land Mobile Network (VPLMN)) is the vPCRF (visited policy control and charging rules function entity). In the scenario of home routed, the PCEF is in the home network, and if there is a BBERF, the BBERF is in the visited network. In the roaming scenario of local breakout, the PCEF is in the visited network, and if there is a BBERF, the BBERF is also in the visited network.
At present, the scheme for implementing the S9 roaming interface is for each UE, the vPCRF terminates the Gx session and Gxx session existing in the visited network of all the IP-CAN sessions established by the UE, and one S9 session is used to transmit the information of the Gx session and Gxx session of all the IP-CAN sessions; however, it does not terminate the Rx session of all the IP-CAN sessions in the visited network, and just forwards the messages of the Rx session to the hPCRF, in which the vPCRF is taken as a proxy. There might be a plurality of subsessions (called S9 subsessions) in one S9 session. Each subsession is used to transmit the information of the Gx and Gxx sessions of one IP-CAN session. When the hPCRF sends the policy control information to the vPCRF, and if the information is issued in the command level (that is, the information is not included in any subsession), the vPCRF considers that the information will be applied to all the IP-CAN sessions of the UE; and if the information is issued in the subsession level (that is, the information is included in the subsession), the vPCRF considers that the information is only used to the IP-CAN session corresponding to the subsession. At present, the hPCRF only can issue the bearer control modes in the command level, which limits that the hPCRF has no ability of deciding different bearer control modes for different IP-CAN sessions of the UE according to the subscription information, the network policy and the network ability. For example, the UE establishes two IP-CAN sessions, and the two IP-CAN sessions select two GGSNs, while the abilities of the two GGSNs are inconsistent. One GGSN supports the bearer establishment initiated by the network, but the other GGSN does not support. Therefore, the bearer control modes selected by the PCRF for the two IP-CAN sessions might be different. Of course, The PCRF can also select different bearer control modes according to the difference of the PDN networks to which the two IP-CAN sessions access, which depends on the network policy.
The defect of the above scheme is that, the hPCRF have no ability of adopting different bearer control modes for different IP-CAN sessions of the UE according to different access network capabilities, which is caused in the multi-access scenario. Multi-access supports that the UE accesses various PDNs through different P-GWs by a variety of access networks at the same time. As shown in FIG. 4, the UE accesses the PDN1 and PDN2 through the non-3GPP IP access network and 3GPP access network simultaneously under the coverage of the non-3GPP access and the 3GPP access. As the network abilities of the access networks are different (for example, one network does not support the bearer establishment initiated by the network, and so on), different bearer control modes should be applied for the PDN connections accessed and established by the UE through different access networks, however, the hPCRF cannot configure different bearer control modes for the PDN connection.